Dropdown menu in After effects with ExtendScript

Hi guys, I,m really new to Extended script. It seems as if theres not alot of tutorials for this software. I just bought the David Torno class for extendedscript to help myself making my own UI panels / Scripts.

Okay, so one of the quesitons I didn't find any anwer for yet is:

I want to do a script panel in which there is a drop down menu, with lets say 3 colors (yellow, red, blue). Those colors would be associated with a layer in a composition. When a color is selected, then it mutes the other two layers:

e.g:. yellow is selected in the UI panel, then it turns off red and blue (they become invisible or we trigger the opacity to 0)... when blue is seletec yellow and red are 'muted' and then so we only see the blue layer, and vice-versa.

I don't ask for you guys to script it, but if you could only refer me to any documentation on dropdowns, how to create them and populate them, i would really appreciate it 😃